Expandable antenna

ABSTRACT

The invention relates to a large expandable antenna or reflector which can be packaged in a small volume. The antenna can be parabolic, spherical or flat. Radial ribs, interconnected in a scissorslike pattern, extend from a center hub. One set of the elements are fabricated to the desired reflector contour while the alternate elements are straight elements which deploy and support the contour elements. A flexible screen or reflector surface between the contoured elements provides the reflector surface.

United States Patent Inventors Robert R. Cannan Tallmadge; Howard W. Barrett, Akron, both of Ohio App]. No. 21,745 Filed Mar. 23, 1970 Patented Dec. 28, 1971 Assignee Goodyear Aerospace Corporation Akron, Ohio EXPANDABLE ANTENNA 7 Claims, 7 Drawing Figs.

11.8. CI 343/915 Int. Cl H0lq 15/20 Field of Search 343/840,

[56] References Cited UNITED STATES PATENTS 3,496,687 2/1970 Greenberg et al. 343/915 2,945,234 7/1960 Driscoll 343/915 3,174,397 3/1965 343/915 3,406,404 10/1968 343/915 3,509,576 4/1970 McLain 343/840 Primary Examiner-Eli Lieberman Attorneys.l. G. Pere and L. A. Germain PATENTEU BEB28 :sn

SHEET 2 [IF 4 mvsmons HOWARD W BARRETT ROBERT R. CARMAN ATTORNEYS PAIENTED M628 1971 SHEET 3 [IF 4 FIG.3

INVENTORS ATTORNEYS Pmzmmmzemn Y 3.631.505

SHEET [1F 4 ATTORNEYS EXPANDABLE ANTENNA Heretofore it has been known that there have been many and various types of packageable antennas which may be deployed from a small packaged configuration to a larger reflective configuration. Certain of these antennas have utilized a lazy tong construction for deployment such as U.S. Pat. No. 1,851,178, 1,689,337, and 3,213,457. However, none of these prior art structures have included the ability to achieve a predetermined surface contour through such lazy tong structure for deployment. Hence, their adaptability to large complex curved reflectors is not apparent or possible.

Therefore, it is the general object of the invention to provide a large expandable antenna or reflector which can be packaged in a small volume that utilizes a lazy tong deployment structure, but wherein the reflector surface can be parabolic, spherical or flat.

A further object of the invention is to provide a low-cost, packageable, but highly reliable expandable antenna that will achieve a high degree of precision in its reflective service upon expansion.

The aforesaid objects of the invention and other objects which will become apparent as the description proceeds are achieved by providing an expandable antenna which comprises a plurality of linked arms arranged in pairs as a lazy tong, a plurality of such lazy tongs arranged in radially directed equally spaced manner about a central point, means to effect controlled extension and retraction of the linked arms from the ends adjacent said center point, one pair of linked arms of each set of lazy tongs defining a predetermined complex shape when fully extended, and the other pair of linked arms having a greater extended length and effecting supporting action of said one pair of linked arms, and flexible reflector means connected between said one pair of linked arms to form a reflective surface when said arms are fully extended.

For a better understanding of the invention, reference should be had to the accompanying drawings wherein FIG. I is a perspective view of the antenna of the invention in the fully stowed relationship in a suitable storage container;

FIG. 2 is a perspective view of the antenna of FIG. 1 in the partially deployed condition;

FIG. 3 is a perspective view of the antenna of FIG. 1 in the fully deployed condition;

FIG. 4 is a perspective view of the antenna of FIG. 1 showing a single lazy tong arm in the fully deployed position;

FIG. 5 is an enlarged side elevational view of the hinged relation of the set of links defining the contoured configuratron;

FIG. 6 is an enlarged view of the adjustable relationship of the supporting links; and

FIG. 7 is a schematic view of the link relationship showing how the pivoted position of the supporting links must be determined.

With reference to the embodiment of the invention illustrated in the drawings, the numeral 10 indicates generally a packageable antenna which in its stowed condition can be carried inside a small cylindrically shaped container 12 for example. Essentially, the structure of the antenna 10 comprises a base hub 14 which normally may be fixed to the base 14a of the container 12. A movable hub 16 is provided which may preferably be guided in a movable parallel relationship to hub 14 by slidably engaging a plurality of rods indicated generally by numeral 18 extending perpendicularly from the surface of hub 14. The rod package 18 will slidably be received through appropriate holes in the hub 16. The invention preferably contemplates that the adjustable relationship of hub 16 with relation to hub 14 may be achieved by a long screw 20 threadably received through the axis of hub 16 and rotatably driven in controllable relationship by a motor 22 carried by the base hub 14. Hence, it should be understood that rotation of a screw 20 in either direction will cause a slow but highly powerful controlled movement of hub 16 relative to hub 14in either an outward or inward direction depending upon the direction of rotation of screw 20.

The invention contemplates that in order to prevent damage to the movable hub 16 and to the overall structure that appropriate microswitches 24 and 26 be mounted on the top of the triangular rod frame 18 and the base hub 14, respectively, as most clearly seen in FIG. 3. These switches 24 and 26 stop the motor 22 as the movable hub reaches and closes these switches during the movement thereof.

The essence of the invention is achieved by utilizing the base structure defined above with a plurality of lazy tong arrangements, each indicated generally by numeral 30. These lazy tong arrangements are radially directed with respect to the hubs at substantially equal spaced angular positions, as best seen in FIG. 4.

Each of the lazy tongs comprises a series of levers pivotally linked at their ends in the usual lazy tong configuration. One set of levers is indicated generally by the numeral 30 with the other set indicated generally by numeral 32. Preferably, the invention contemplates that the levers will be made of metal and the set 30 will be pivotally connected at their radially inward end to the movable hub 16. It also should be noted that the pivoted end of the levers 30 is enlarged and angled as at 30a so as to facilitate pivotal movement through relatively large angles. Also, it should be noted as illustrated in FIG. 6, that the ends 30a are adjustably mounted to hub 16 by screws 31. This adjustability allows proper alignment of the levers 30 so that the configuration of levers 32 will be proper, as more fully defined hereinafter.

The set of levers 30 are pivotally connected at their ends by pins 30b, while the set of levers 32 are pivotally connected at their ends by pins 32b. The lever sets 30 are pivotally connected at about their center points to about the center points of levers 32 by appropriate pins 34. The exact relation between levers 30 and 32 will be defined hereinafter with reference to FIG. 7. The lever sets 32 are fabricated to a desired reflector contour while the other set of levers 30 are straight elements which deploy and support the contour elements 32. Hence, in the example illustrated, the levers 32 are contoured to a parabolic shape in their fully extended condition of FIG. 3. It can be seen that the levers 30 are longer and hence are not fully extended when the lever set 32 is fully extended so that quite firm and adequate support of the contoured levers 32 is achieved by the levers 30 by somewhat of a truss arrangement. A reflective surface is provided by connecting a flexible screen between adjacent contoured lever sets 32 so that this stretches tightly into position, as illustrated in FIG. 3, when the levers are fully extended. In order to more easily permit the flexible reflective material 50 to be attached to the edges of levers 32 without interferring with the movement of levers 30, the levers 32 are preferably made of parallel spaced side-by-side elements 320 and 32d, respectively, as is most clearly illustrated in FIG. 4 of the drawings, so that levers 30 can be pivotally received therebetween.

The parabolic reflector achieved by the flexible screen 50 between lever elements 32 is not bothered by the radial protrusion of those portions of levers 30 which extend above the surface thereof. Further, the invention contemplates that when the levers 32 are moved in from their lazy tong arrangement to the packaged configuration of FIG. 1 by the upward movement of hub 16, that such curved levers or lengths 32 will tend to flatten to the straight line configuration of levers 30. This is accomplished by designing the levers 32 with a cross section to limit the induced stresses so that when flattened, they will be of value less than the yield stress of the material. This permits flattening when packaged to the configuration of FIG. 11, and a return to their parabolic curved configuration when extended to the full length by the lazy tong achieved by the movement of hub 16.

Naturally, while the invention discloses a flexible screen reflector, any flexible material which might be designed to reflect electromagnetic or radio waves, or solar energy, might also be appropriately utilized. For example, some type of aluminized thin plastic sheet might be utilized for a solar reflective surface.

While the invention illustrates that the levers or elements 32 are double parallel bars 320 and 32d, the invention contemplates that any suitable type of construction to achieve the lazy tong relationship with a suitable curvature of the elements 32 and still allowing the attachment ofa flexible skin to the adjacent edges will certainly meet the objects of the invention. For example, a single lever with a small slot in the center thereof would achieve the same results as the double elements 32c and 32d. However, even if the levers 30 are pivotally attached outside the edges of levers 32, the flexible skin may simply extend therearound and accomplish the purposes of the invention.

FIG. 5 illustrates a spring loading of the elements 32. Essentially, this is achieved by providing a coiled spring 33 surrounding the hinge pins 32b and normally biasing the elements 32 to the open contoured position. Also, the invention contemplates that the hinge 32b may be of the type that limits the angular rotation between the elements 32 in the open direction and preferably limits this opened relationship to about 180 or slightly less to approximate the curved configuration between the elements 32.

FIG. 6 illustrates the adjustable pivoted relation of the ends 30a of levers 30. Essentially the screw 31 is adjustable in height in relation to hub 16 by means of nuts 31a and 31b respectively. The adjustment of the pivot point of the end lever 30 in effect controls the extension and contoured height of elements 32. Hence, this adjustability is important.

FIG. 7 schematically illustrates the lazy tong at its fully extended position to achieve the necessary curvature of the elements 32. It is an important feature of the invention that the pivot points 30b for levers 30 fall on lines essentially perpendicular to the pivot points 32b of elements 32 as illustrated. The pivotal connection of levers 30 to elements 32 then falls wherever they cross, as dictated by the pivotal connection of the ends of levers 30 on the perpendiculars indicated by lines 29 in FIG. 7. If the levers 30 are not so pivotally connected then the elements 32 will not properly unfold into the desired lazy tong configuration.

Hence, it is seen that the objects of the invention have been achieved by providing a lazy tong relationship with a fixed hub and a movable hub, limiting switches associated with the hub to control the extendable movement of the lazy tong, and wherein one of the sets of each lazy tong is shorter than the other, and has a contoured configuration so that when extended a desired shape and total around a central hub is achieved. It should be noted however, that the means to extend the lazy tong configuration is not important, except that some suitable means must be provided.

While in accordance with the patent statues only the best known embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby, but that the inventive scope is defined in the appended claims.

What is claimed is:

1. An expandable antenna which comprises a pair of support hubs,

means to controllably move the hubs relative to each other,

a pair of sets linked arms arranged as a lazy tong structure having the end of one set of arms pivotally mounted to one hub, and the end of the other set of arms pivotally mounted to the other hub, which is characterized by the sets of arms defining the lazy tongs arranged in equally spaced radial relation around the entire circumference of the hubs, one set of arms of each such lazy tong defining a predetermined contour when extended to their full length, said other set of arms of each said lazy tong having a greater extended length and serving to support the fully extended length of said one set of arms, and

flexible reflector means attached between adjacent said one sets of arms which stretches tight to the contour of said one set of arms when extended to in combination define a desired contoured reflective surface, said contoured reflective surface being the same as would be geometrically generated by rotation of said one set of arms when extended about an axis through the center ofthe planes of the pair of hubs and normal thereto.

2. An antenna according to claim 1 where one of the hubs is fixed and the other hub is movable relative to the first hub, which includes a screw connecting said one hub in relative relation to the fixed hub, means to effect rotation of the screw, and means to limit rotation of the screw upon predetermined movement ofsaid one hub relative to the fixed hub.

3. An antenna according to claim 1 where said one set of arms has each length thereof performed to a predetermined contour, but where in the collapsed relationship of the lazy tong, said one set of arms is flattened to a straight configuration which is less than the yield point of the material of the arm.

4. An expandable structure which comprises a set of linked contour arms and a set of linked support arms arranged in pairs as a lazy tong, a plurality of identical such lazy tongs arranged in a radially directed equally spaced manner around a central axis, means to efl'ect controlled extension and contraction of the linked arms from the ends adjacent said central axis, the set of linked contour arms of each lazy tong defining a predetermined contour when fully extended, said contour falling in the surface of a contoured figure generated by rotation of a set of fully extended linked contoured arms about said central axis, and the set of linked support arms having a greater extended length and forming triangular support for said set of linked contour arms at their fully extended length, and flexible means connected between every set of linked contour arms, said flexible means forming a contoured surface the same as generated by rotation of the fully extended set of linked contour arms around the central axis when said sets of linked contour arms are fully extended.

5. A structure according to claim 4 where the pivot points of the other set of linked arms lie on a line extending substantially perpendicularly from the pivot points of said one set of linked arms according to the contour defined thereby when fully extended.

6. A structure according to claim 4 where spring bias means are associated with all the pivot points of said one set of linked arms tending to bias such arms to the open fully extended position.

7. A structure according to claim 4 where said one set of linked arms has structural characteristics so as to be bent flat when in the folded condition without exceeding the yield strength of the material thereof. 

1. An expandable antenna which comprises a pair of support hubs, means to controllably move the hubs relative to each other, a pair of sets of linked arms arranged as a lazy tong structure having the end of one set of arms pivotally mounted to one hub, and the end of the other set of arms pivotally mounted to the other hub, which is characterized by the sets of arms defining the lazy tongs arranged in equally spaced radial relation around the entire circumference of the hubs, one set of arms of each such lazy tong defining a predetermined contour when extended to their full length, said other set of arms of each said lazy tong having a greater extended length and serving to support the fully extended length of said one set of arms, and flexible reflector means attached between adjacent said one sets of arms which stretches tight to the contour of said one set of arms when extended to in combination define a desired contoured reflective surface, said contoured reflective surface being the same as would be geometrically generated by rotation of said one set of arms when extended about an axis through the center of the planes of the pair of hubs and normal thereto.
 2. An antenna according to claim 1 where one of the hubs is fixed and the other hub is movable relative to the first hub, which includes a screw connecting said one hub in relative relation to the fixed hub, means to effect rotation of the screw, and means to limit rotation of the screw upon predetermined movement of said one hub relative to the fixed hub.
 3. An antenna according to claim 1 where said one set of arms has each length thereof performed to a predetermined contour, but where in the collapsed relationship of the lazy tong, said one set of arms is flattened to a straight configuration which is less than the yield point of the material of the arm.
 4. An expandable structure which comprises a set of linked contour arms and a set of linked support arms arranged in pairs as a lazy tong, a plurality of identical such lazy tongs arranged in a radially directed equally spaced manner around a central axis, means to effect controlled extension and contraction of the linked arms from the ends adjacent said central axis, the set of linked contour arms of each lazy tong defining a predetermined contour when fully extended, said contour falling in the surface of a contoured figure generated by rotation of a set of fully extended linked contoured arms about said central axis, and the set of linked support arms having a greater extended length and forming triangular support for said set of linked contour arms at their fully extended length, and flexible means connected between every set of linked contour arms, said flexible means forming a contoured surface the same as generated by rotation of the fully extended set of linked contour arms around the central axis when said sets of linked contour arms are fully extended.
 5. A structure according to claim 4 where the pivot points of the other set of linked arms lie on a line extending substantially perpendicularly from the pivot points of said one set of linked arms according to the contour defined thereby when fully extended.
 6. A structure according to claim 4 where spring bias means are associated with all the pivot points of said one set of linked arms Tending to bias such arms to the open fully extended position.
 7. A structure according to claim 4 where said one set of linked arms has structural characteristics so as to be bent flat when in the folded condition without exceeding the yield strength of the material thereof. 